Não informado. (1976). Minerals & Materials. U.S. Department of the Interior, Bureau of Mines.
Chicago (17e ed.) BronvermeldingNão informado. Minerals & Materials. Washington: U.S. Department of the Interior, Bureau of Mines, 1976.
MLA (8e ed.) BronvermeldingNão informado. Minerals & Materials. U.S. Department of the Interior, Bureau of Mines, 1976.
Let op: Deze citaties zijn niet altijd 100% accuraat.